1. Field of the Invention
The present invention relates to an induction charging apparatus for use in various kinds of electric apparatuses such as, portable game machines, power-driven tooth brushes, electric tools, or the like and, more particularly, to an induction charging device having a power source unit and a battery unit detachably connected to the power source unit for the supply of electric power from a commercial power source through the power source unit to the battery unit, utilizing the electromagnetic induction coupling between the power source unit and the battery unit.
2. Description of the Prior Art
In the conventional arrangement of induction charging apparatuses of the aforementioned type, a secondary battery (rechargeable battery) is installed in a unit of the device. Normally, the unit of the device is set to a power source and prepared to stand a short-term driving load while the secondary battery is kept charged with a minute current from the power source. Therefore, a primary oscillator section, e.g., an inverter circuit or the like at the side of the power source is always held in the driving state, and at the same time, the output of the primary oscillator section is controlled depending on the presence/absence of the load in the device unit so as to save power in case the device unit is separated from the power source for a long time.
In the arrangement as above, in the case where the available output power from the primary oscillator section is increased and if a metallic element such as a clip or the like, instead of the device unit, is brought close to a primary coil, the metallic element is erroneously recognized as a proper load. In consequence, an excessive amount of eddy current is fed and heat is generated.
The inventors have discovered from the studies of the aforementioned inconvenience that, when the primary oscillator section is maintained always in the driving state and the primary coil is accommodated in the power source unit while being separated from a touching face thereof to the power source, the magnetic flux density at the peripheral surface of a main casing can be made as small as possible, and moreover, if a touching face of the power source is made movable to the primary coil in the interlocking movement with setting of the device unit to the power source, the above inconvenience is perfectly solved.